Automatic telephone system



Patented May 14, 1940 UNITED STATES PATENT QFFECE AUTOMATIC TELEPHONE SYSTEM Application June a, 1928, Serial No. 211,579

14 Claims.

This invention relates generally to automatic telephone systems and more particularly to circuit arrangements for controlling the release of the automatic switches used in establishing connections in such systems.

In automatic telephone systems it is ordinarily quite impossible for a called subscriber to identify a calling subscriber unless the calling party willingly identifies himself. Telephone subscribers are occasionally annoyed by anonymous calls whose source it is desirable to determine in order to terminate the annoyance. For this purpose a number of systems have been developed which accomplish the desired result but require special equipment in the regular switching circuits.

Another fault of systems of this nature known to applicant, is the necessity for connecting the call-holding equipment to the private or control conductor of the connector bank contacts as- 20 sociated with the subscribers line. This concluster is ordinarily accessible only at the line relay equipment which, in the case of a large exchange, may occupy considerable space. In order to permit the connection of the call-holding equipment of said systems to the line of any subscriber in the exchange it has been necessary in some instances to run a five-conductor cable from each call-holding circuit to every line equipment board in the exchange. This addsto the 30 expense of installation besides greatly complicating the wiring arrangements between the callholding equipment and the subscribers lines.

It is accordingly an object of the invention to provide improved circuit arrangements to permit a called subscriber to trap or hold a so-called annoyance call untilthe switchroom. attendant can trace the call to its source to determine the line from which it was made. It is a further object of the invention to provide improved circuit ar- 40 rangements of this type for temporary inclusion in the line of any subscriber who may be annoyed by anonymous calls. It is a further object to provide a call-holding circuit that maybe temporarily associated with the line of any subscriber without requiring any change or alteration in the circuits of the switching equipment. It is a still further object of the invention to improve the operation of such equipment, to reduce the cost of the initial installation, and to render it simply 50 and easily available to any subscriber in the exchange.

It is a still further object to eliminate the necessity for a connection from the control conductor of the switch train to the call-holding equipment and, by so doing, to make it possible to connect the call-holding equipment in series with a subscribers line at the main distributing framev where all of the exchange lines are easily accessible and where existing connections between subscribers lines and the switching equipment may be readily altered to permit the temporary inclusion of call-holding equipment in the subscribers line.

Other objectsand features will be more fully described hereinafter in connection with the accompanying drawing, which shows diagrammatically a telephone exchange system including the features and detailed circuits of applicants invention.

The automatic telephone system shown in the drawing includes a calling subscribers station indicated at A connected to the central exchange equipment by means of line conductors l. The subscribers line is connected to a line circuit 3 by way of the main distributing frame and jumper connections 2. The line circuit equipment may be of any well known type and serves to initiate the operation of the calling end of the link circuit 4 to search for and connect with a bank contact corresponding to the calling subscribers line. r

The link circuit 4 may conveniently comprise a well known type of finder-selector link arranged to connect the calling subscribers line. with an adle connector switch upon the operation of the subscribers calling device.

The connector switch indicated at'ii may be any well known type of final selector switch mechanism, the only requirement being that the connector must be arranged to maintain all preceding switches in the train in their operated positions until the release of the connection by the calledsubscriber. Such a connector is shown in the Peterson Patent No. 2,040,153, granted May 12, 1936. This patent shows two connector switches, one of a standard widely used type and the other, a modification of the first, arranged to prevent certain unauthorized operations. Either of these connectors as well as others performing similar functions may be used in app-licants system.

The banks of the connector switch are connected to the main distributing frame and thence to subscribers lines such as 8 in the usual manner. the detailed circuit arrangement of applicants improved call-holding repeater, the operation of which will now be described in .detail.

One or more call-holding repeaters such as the one shown may be connected by means of a cable The remainder of the disclosure consists of to the main distributing frame at which point it may be temporarily connected in the line of any subscriber desiring such service, by means of the cross-connecting jumper 9, in which case the jumpers 6 would be disconnected.

Let it be assumed that a calling subscriber such as A has caused the extension of a connection from his substation to the connector bank contact corresponding to the line of a called sub scriber, such as B, and the switching equipment is now prepared to signal the called subscriber. The connector circuit 5 now transmits interrupted ringing current of suitable frequency over one or the other of the talking conductors of the line. This alternating ringing current is extended to the call relays II and I2 of the call-holding repeater by way of one of the left-hand conductors I. Two call relays I I and I2 are provided, one being connected to each side of the line to permit the use of divided ringing. One of the relays II or I2 operates from the ringing current transmitted from the connector.

If the ringing current is connected in the connector to the negative side of the line, relay I2 will operate by way of the back contact associated with armature 25 of the release relay I4. At armature 2!, relay l2 closes a circuit for bypass relay I6 which thereupon operates. Relay I6, upon operating, extends the negative and positive conductors by way of make contacts 30 and 32 to the line of the called subscriber, thereby extending the ringing current thereto and causing the operation of the called subscriber's ringer. In addition to completing the ringing circuit as described, relay I6 also closes a circuit at armature 3| for relay I1. Relay I1 is of the type which has a weight attached to its armature spring, whereby the armature spring is caused to vibrate between the fixed contact on either side thereof when the magnet is deenergized.

Relay I'I, upon operating, completes a circuit at armature 33 for relay I8, which also operates. Relay I 8, upon operating, at armature 34 prepares an energizing circuit for the trap relay I9. At armature 35, relay I8 prepares a locking circuit for itself,'which, however, does not become effective until the called subscriber answers. At armature 36 relay I8 also prepares a loop circuit by way of the repeating coil RC and make contacts 25 and 28 of the release relay I4, which also does not become completed until the response of the called subscriber. When the ringing current is disconnected at the end of the first half ringing cycle relay I2 releases and opens the circuit to relay I6 which in turn opens the circuit to relay When relay I1 is deenergized, its armature 33, by virtue of the weight attached thereto, vibrates rapidly between the fixed contacts, thus intermittently closing and opening the circuit to relay I8. Relay I8 is somewhat slow to release and remains operated during the interruptions of its circuit. When ringing current is again connected to the negative line conductor relays I2 and I6 again operate in turn to hold relay I1 steadily operated. Relay I1 is so constructed as to maintain relay I8 operated during, the entire silent portion of the ringing cycle.

The operation of relay [8 is without effect at this time, but prepares certain circuits previously described subject to the response of the called subscriber. This particular arrangement of the hold relays I I and I8 is a feature of the invention which makes possible the attainment of one of theobjects, namely, the reduction in the number of cable conductors required to place the callholding repeater in service. When the called subscriber at substation answers the call by removing his receiver, a connection is made across line conductor 8 to cause the operation of line relay I3, provided the subscriber answers during the silent portion of the ringing cycle when relays I2 and I6 are deenergized. If the subscriber answers the call during the time that ringing current is being applied, the sequence of operations will be somewhat different, as will be described later. Line relay I3 operates over both of its windings in series by Way of the right-hand windings of the repeat- I ing coil RC, the normally closed contacts associated with armatures 36 and 32 of relay I6, the

negative and positive line conductors included in the cable I, the right-hand jumpers 9 and line conductors 8 through a closed circuit at subscribers station B. Line relay I3, upon operating, closes a further point in the circuit for the upper winding of trap relay I9 at armature 22, this circuit, however, being held open by contact 29. At'armature 23, the line relay. I3 closes a circuit for release relay I4. At armature 24 a circuit is prepared to include the left-hand wind-. ings of the repeating coil RC in a bridge across the incoming line conductors from the connector banks. This circuit,'however, is not immediately closed, being held open at contacts 25 and 28 during the operating time of release relay 'I4. Relay I4, having operated immediately after line relay I3, a bridge circuit is now closed across the line conductors extending to the connector. 4

lay of the connector circuit in a well known manner to terminatethe transmission of ringing 1 current and. to maintain the connector switch and all preceding switches in the train in their operated positions.

Release relay I4, upon operating, in addition to completing a loop circuit to the connector banks, prepares a circuit for the winding of series relay=I5 at armature 26. At armature 21 relay I4 closes a locking circuit for relay I8 which had been held energized by the vibration of the armature 33 of relay IT. The substations A and B are now electrically connected and the subscribers thereat may engage in conversation.

As previously mentioned if the called subscriber at substation B removes his receiver at a time when ringing current is applied to the line the sequence of operation will differ somewhat from that described previously. Since relay I6 is at this time operated, the closing of the loop circuit across conductors 8 results first in the energization of the ring-cut-ofi. relay of the connector followed in turn by the energization of the back-bridge or battery feed relay also in the connector 5. When the ring-cut-off relay operates it disconnects the ringing current from the line conductors to cause the release of relay I2, which in turn'deenergizes relay I6. When relay I6 falls away after a short interval the circuit to. the back bridge relay of the connector is opened momentarily at armatures 36 and 32. A bridge circuit including the winding of repeating coil RC is subsequently reclosed upon the energization of line relay l3 and release relay M, as previously described, to reoperate the back bridge relay, the ring-cut-oif relay having locked itself in a local circuit. This momentary interruption of the circuit to the backbridge relay results only in a slight unobjectionable click in the receiver of the calling subscriber, but does not interfere with transmission since the backbridge relay will be again operated by the operation of line relay l3 and release relay l4 before the called subscriber has had time to replace his receiver to his ear. This feature, while not particularly objectionable, could easily be corrected by slight alterations in the circuit arrangement, such changes being entirely within the skill of a capable engineer.

If the subscriber at substation B has no reason to lock up this established connection he merely replaces his receiver when the conversation is finished to release line relay 5% followed in turn by release relay M and relay 18. If the calling subscriber at substation A has already replaced his receiver the opening of contacts 2d of the line relay 13 results in the release of the connector switch 5 of all preceding switches in the train to their normal positions in readiness for another call.

If, however, the subscriber at substation A is unknown to the subscriber at substation B and has been annoying him, the subscriber at substation E operates his calling device to transmit a single impulse, or momentarily depresses the hook-switch of his telephone instrument, to cause the momentary release of the line relay l3. This operation is sufiicient to cause the energization of trap relay It to signal the supervisory operator or other attendant that a call isheld and is to be traced to its source. In detail, the operation is as follows: When line relay l3 releases in response to the dialling of the single digit, the original energizing circuit for release relay Hi is opened. Relay [4, however, being slow to release, remains energized during the time line relay I3 is deenergized responsive to the dialled impulse. A circuit is therefore closed by way of the back contact associated with armature 23 and the make contact associated with armature 26, to the winding of series relay I5. Relay I5- operates and remains operated for a short interval after line relay 3 is reoperated. A circuit is then completed by way of armature 22 of the line relay l3, armature 29 and its associated make contact, armature 34 and its makecontact, to the upper winding of trap relay l9. At armature 23 the circuit to the winding of the series relay i5 is opened and the release relay It is again energized.

Relay l9, upon operating, closes a locking circuit for its lower winding by way of armature 37 and the normally closed release key 4|. Relay 19 therefore remains operated independent of the series relay 15 which now restores to its normal position. At armature 38, relay I9 closes the cir-: cuit for the alarm lamp 42 which is located at the desk of a supervisory operator or some other suitable attendant, to indicate that a call has been held and, should be traced to determine its source.

Contact 35 controlled by the hold relay I8 is provided to shunt contacts 2% of the line relay 13 in order to prevent any interruption of the circuit to the back-bridge relay of the connector, when the subscriber operates his calling device. to momentarily release the line relay and indi-v cate that the call is being held,

The called subscriber at substation B understands that after having caused the signal to be transmitted to the operator, he is required to remain connected to the line until the operator or attendant communicates with him to indicate that he has received the signal and has taken over supervision of the connection.

When the attendant sees the lighted alarm lamp 52, he operates monitoring key 39, to con meet his telephone set ii) to the line conductors of the called subscriber by way of contacts %3 and 44 of the operated relay 19. The attendant now communicates with the called subscriber to inform him that he may now replace his receiver.

At this time the line relay I3 is held operated by way of the monitoring key 39 and the telephone set 4i! to prevent the release of connector 5 which in turn holds all preceding switches energized regardless of any action on the part of the subscriber at substation A. The attendant may now trace the call back over the operated switches in a well known fashion. When identification of the calling partys line has been made, the attendant momentarily operates release key 4| to unlock trap relay !9, which in turn releases line relay It to restore all relays in the repeater circuit and all of the switches of the train to their normal positions in readiness for a further call.

When the subscriber at substation B desires to make a call, the operation of the switching equipment takes place just as though the callholding' repeater were not present. When subscriber B removes the receiver from his telephone instrument line relay i3 is energized over a loop circuit including the right-hand winding of repeating coil RC, the normally closed contacts associated with armatures 30- and 32, negative and positive line conductors included in the cable 1, the right-hand jumper connections 5, and the line 8. The operation of line relay 3, at armature 23, causes the operation of release relay i l. The closing 01' contacts 22 is without efiect at this time, since further points in the circuit are opened at armatures 2S and 36. Armature it prepares a loop circuit to the line circuit of the switching equipment which circuit includes the lefthand windings of the repeating coil RC and the operated contacts associated with armatures 25 and 28 of release relay M, which has now operated. A second line circuit similar to the line circuit 3 and individual to the line of subscriber B is connected to the three conductors at the right of the connector 5 as indicated. This line circuit is connected to a further link circuit and connector, such as is shown in connection. with subscriber A.

The closing of the loop circuit as previously described prep-ares the switching equipment for the reception of dialled impulses. When subscriber B operates his calling device to set the switching equipment, line relay I3 is intermittently released, opening contacts 2% to repeat the dialled impulses to the switching equipment. Release relay l4 being slow to release, remains energized during the dialling period. During the time the line relay i3 is alternately released and reoperated, series relay l5 isoperated as previously described. The operation of this relay is, however, without effect, since the circuit partially controlled by contacts 223 still remains open at armature 34.

- When the conversation has terminated and the subscriber B replaces his receiver the loop circuit previously described is opened to cause the release of line relay I3 and the subsequent release of release relay l4, opening the circuit to the switching equipment and restoring all relays and switches to their original positions provided the called subscriber has also replaced his receiver.

It is obvious that subscriber E cannot hold a call which he himself makes, since no provision is made for the operation of hold relays I! and i8 or the trap relay 19 in this case.

Although applicants improved call-holding repeater circuit has been illustrated as applied to a small automatic system of 1000 lines or less, it will be understood that the invention is applicable to systems of any size and of practically any nature. The application of the invention may be made to any system of a similar nature without requiring any alterations in the existing peater between said switching equipment and any one of said subscribers lines, said means including electrical conductors, not to exceed two in number, connecting the repeater to the switching equipment.

2. In a telephone system having automatic switching means for telephonically interconnecting two subscribers, a self-contained call-holding repeater, means for operatively connecting said repeater between said switching means and any one of said subscribers lines, said connecting means including a plurality of terminals on the repeater and electrical conductors jumpered to a group of said terminals, not to exceed four in number, from said switching means and from the line of said one subscriber, and means in said repeater controlled exclusively by said one subscriber when said subscriber is the called party for displaying a characteristic signal.

3. In a telephone system having automatic switching equipment for telephonically interconnecting two subscribers, a call-holding repeater, means comprising only four electrical conductors for operatively connecting said repeater between said switching equipment and any one of saidrsubscribers lines, only two of said conductors connecting the repeater to the switching equipment, an operators position, and means in said repeater controlled exclusively by said one subscriber only when saidsubscriber is a called party for connecting his line to said operators position. 1

4. In a telephone system having automatic switching equipment for telephonically interconnecting two subscribers, a call-holding repeaten' means comprising only four electrical conductors for operatively connecting said repeater between said switching equipment and any one of said subscribers lines, two of the conductors connecting the repeater to the switching equipment and the other two conductors connecting the repeater to said one line, an operators position, and means in said repeater controlled exclusively by a called subscriber, to whose line said repeater is phone equipment at said position to said called subscribers line;

5. a telephone system having automatic switching means for telephonically interconnecting two subscribers, a call-holding repeater, means for operatively. connecting said repeater between said switching means and any one of said subscribers lines, said connecting means including not more than two electrical conductors connecting the repeaterto the switching means and not morethan two other electrical conductors connecting the repeater to said line, an operators position, means in said repeater controlled exclusivelyby a called subscriber, to whose line said repeater is connected, for signalling the operator at said position and for connecting the operators telephone equipment at said position to said called subscribers line, and means controlled exclusively by the operator at said position for extinguishing said signal and for releasing the connection extended to the called line over said switching means.

6. In a telephone system having automatic switching equipment for connecting the line of a calling subscriber to the line of a called subscriber, said switching equipment being partly controlled over a control conductor extending therethrough, means including a call-holding repeater for preventing the release of said switching equipment, said repeater controlling said switching equipment independently of said control conductor, and arranged to be temporarily connected to the line of said called subscriber.

7. In a telephone system having automatic switching means for connecting the line of a calling subscriber to the line of a called subscriber, a call-holding repeater included in connections extended to the line of said called subscriber over said switching means, a circuit extending through said repeater for the transmission of speech therethrough, said repeater being controllable by said called subscriber solely over said speech transmission circuit to prevent the release of said switching means, said repeater controlling said switching means solely over said speech transmission circuit.

8. In a telephone system having automatic switching equipment for connecting the line of a calling subscriber to the line of a called subscriber and signalling means arranged to actuate a signalling device connected to the line of said called; subscriber, said signalling means being alternately effective and ineffective whereby said signalling device is intermittently operated, a call-holding repeater connected to the line of said called subscriber, a relay insaid repeater operated during the effective period of said signalling means, and means independent of said switching equipment and said signalling means for maintaining said relay operated during the ineffective periods of said signalling means.

9. In a telephone system having automatic switching equipment for connecting the line of a calling subscriber to the line of a called subscriber and signalling means arranged to actuate a.

signalling device connected to the line of said called subscriber, said signalling means being alternately effective and ineffective whereby said signalling device is intermittently operated, a

for maintaining said relay operated during the ineffective period of said signalling means, and

means controlled by said called subscriber for maintaining said relay operated independent of said switching equipment, said signalling means and said last-named means.

10. In a telephone system having automatic switching means for interconnecting the line of a calling subscriber with the line of a called subscriber and for signalling said called subscriber by means of an interrupted signalling current, a call-holding repeater associated with the line of said called subscriber, a relay in said repeater arranged to be operated by said signalling current, and means in said repeater for maintaining said relay in its operated position during the interruptions of said signalling current.

11. In a telephone system having automatic switching means for interconnecting the line of a calling subscriber with the line of a called subscriber and for signalling said called subscriber by means of an interrupted signalling current, a call-holding repeater associated with the line of said called subscriber, a relay in said repeater arranged to be operated by said signalling current, means in said repeater for maintaining said relay in its operated position during the interruptions of said signalling current, and means controlled by said called subscriber for maintaining said relay operated independent of said lastnamed means.

12. In a telephone system, a repeater, switching equipment for completing connections to said repeater thereby to extend calls over same, means in said repeater responsive to the answering of a call extended thereover for connecting a bridge across the connection completed to said repeater, said bridge effective to maintain said switching equipment operated to hold said connection so long as said bridge is connected thereacross, a signal associated with the repeater and responfor bridging the connection completed thereto responsive to the bridging of said line, the bridge across said connection effective, so long as same remains across said connection, tomaintain said switching equipment operated and hold said connection, a signal associated with the repeater, means at the substation for transitorily disconnecting the bridge from said line to operate said signal, and means in the repeater for maintaining said bridge across said connection during said transitory disconnection of the bridge from said line.

14. In a telephone system, a repeater having an incoming line and an outgoing line, a bridge in said repeater normally disconnected from said incoming line, means for bridging said outgoing line, means in said repeater for connecting said first bridge to the incoming line responsive to the bridging of said outgoing line, means for thereafter transitorily disconnecting the bridge from said outgoing line, and means for maintaining said first bridge connected to the incoming line during said transitory disconnection of the bridge from said outgoing line.

HANS P. BOSWAU. 

